I had a sidecar for a while, but recently sold it.
I did plug it into my computer to sniff out the MIDI signals it sent out, but it was very confusing until I realized it sent out a series of Midi program change numbers for each function.
For instance, the first time you pressed erase it would send (not actual numbers) PC 1, then 2, 3, 4, 5, 6 and loop back to the first. I was able to control the Boomerang with my computer, but I had to cycle through this list of PC numbers to make it work.
I'll check on my computer when I get home to see if I still have that list, but I didn't investigate it completely, so it will be only a partial listing.
In any case, you'd need a custom MIDI controller to cycle through the list of MIDI PCs with a single button, so arduino DIY controller is the way to go.
Also, Boomerang has a new owner and pedals should be back in production soon (according to website).